Distinct neural correlates for volitional generation and inhibition of saccades.

The antisaccade task has proven highly useful in basic and clinical neuroscience, and the neural structures involved are well documented. However, the cognitive and neural mechanisms that mediate task performance are not yet understood. An event-related fMRI study was designed to dissociate the neural correlates of two putative key functions, volitional saccade generation and inhibition of reflexive saccades, and to investigate their interaction. Nineteen healthy volunteers performed a task that required (a) to initiate saccades volitionally, either with or without a simultaneous demand to inhibit a reflexive saccade; and (b) to inhibit a reflexive saccade, either with or without a simultaneous demand to initiate a saccade volitionally. Analysis of blood oxygen level-dependent signal changes confirmed a major role of the frontal eye fields and the supplementary eye fields in volitional saccade generation. Inhibition-related activation of a specific fronto-parietal network was highly consistent with previous evidence involved in inhibitory processes. Unexpectedly, there was little evidence of specific brain activation during combined generation and inhibition demands, suggesting that the neural processing of generation and inhibition in antisaccades is independent to a large extent.